Utilisation des produits terminaux de la digestion par la mamelle chez la vache laitière

Abstract

Relations between mammary arterio-venous (AV) differences and arterial level were studied for glucose, acetate and beta-hydroxybutyrate on 172 samples and for blood essential amino acids on 20 samples, pooled by day and by cow. The data were obtained from 32 experiments on 5 cows eating various diets (Rulquin, 1981, 1983). AV differences in acetate and beta-hydroxybutyrate were highly related to the arterial levels (R=0.97 and 0.86) and averaged 74 and 41% of these levels (fig. 1). On the other hand, the AV difference in glucose was poorly (R=0.5) related to the arterial levels. Among the essential amino acids, only AV differences in phenylalanine, leucine, arginine, isoleucine and histidine were linearly related to the arterial levels (R=0.78, 0.73, 0.68, 0.63, 0.60) (fig. 2). AV differences in lysine, methionine, valine and threonine were more related to the AV differences of other amino acids than to the arterial levels (fig. 3). These results have been discussed in connection with different mammary metabolic transport systems and with the ability to modify mammary nutrient input by dietary manipulation.